Selective Deprotection of Silyl Ethers

Nelson, Todd D.; Crouch, R. David

doi:10.1055/s-1996-4350

Cited by 265 publications

(212 citation statements)

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“…Reaction of 4-[(tertbutyldimethylsilyl)oxy]-2-butynal (4) [15] with tris(trimethylsilyl)aluminum etherate resulted in an efficient transfer of a nucleophilic trimethylsilyl group [16] by 1,2-addition to the aldehyde; this affords an a-silyl aluminum alkoxide [17] which was trapped in situ with either acetic anhydride or (methoxymethyl)chloride (MOMCl) to provide a-alkoxypropargylic silanes 5 a,b. Selective removal of the TBDMS protecting group by treatment with 10-camphorsulfonic acid (CSA), [18] followed by reaction of the resulting propargylic alcohols 6 a,b with methyltriphenoxyphosphonium iodide gave the corresponding iodides 7 a,b.…”

Section: Resultsmentioning

confidence: 99%

Enantioselective Total Synthesis of Wieland-Gumlich Aldehyde and (−)-Strychnine

et al. 2000

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A total synthesis of (-)-strychnine in 15 steps from 1,3-cyclohexanedione in 0.15% overall yield is described. The sequence followed in the assembling of rings is: E-->AE [2-(2-nitrophenyl)-1,3-cyclohexanedione]-->ACE (3a-aryloctahydroindol-4-one)-->ACDE (arylazatricyclic core)-->ABCDE (strychnan skeleton)-->ABCDEF (Wieland-Gumlich aldehyde)-->ABCDEFG (strychnine). The key steps of the synthesis are the enantioselective construction of the 3a-(2-nitrophenyl)-octahydroindol-4-one ring system and the closure of the piperidine ring by a reductive Heck cyclization to generate the pivotal intermediate (-)-14. In contrast, a Lewis acid promoted a-alkoxypropargylic silane-enone cyclization did not lead to synthetically useful azatricyclic ACDE intermediates. The introduction of C-17 and the closure of the indoline ring by reductive amination of the alpha-(2-nitrophenyl) ketone moiety complete the strychnan skeleton from which, via the Wieland-Gumlich aldehyde, the synthesis of (-)-strychnine is achieved.

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Section: Resultsmentioning

confidence: 99%

Enantioselective Total Synthesis of Wieland-Gumlich Aldehyde and (−)-Strychnine

et al. 2000

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“…[6] The strong affinity of tBu-P4 base for a proton is regarded as being synthetically useful, however the ability of tBu-P4 base to activate silylated nucleophiles has not been shown. [7] Therefore, various catalytic reactions using silylated nucleophiles as precursors of highly nucleophilic anions promoted by tBu-P4 base were non-metallic organic bases. Among them, the tBu-P4 base has been used for various selective deprotonative transformations, although the ability of tBu-P4 base to activate silylated nucleophiles has not yet been shown.…”

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confidence: 99%

Catalytic Activation of Silylated Nucleophiles Using tBu‐P4 as a Base

et al. 2005

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Trialkylsilyl groups play an important role as effective protecting groups in organic synthesis. Various O, N, and C nucleophilic sites can be protected by trialkylsilyl groups to control the selectivity of reactions. The nucleophilic attack of a fluoride anion on a silyl group is recognized as one of the most useful methods for desilylation. The activation of the nucleophile–silicon bond is important not only for desilylation but also for the generation of a reactive nucleophilic anion to achieve a new bond formation. The phosphazene bases developed by Schwesinger are known to be strong non‐metallic organic bases. Among them, the tBu‐P4 base has been used for various selective deprotonative transformations, although the ability of tBu‐P4 base to activate silylated nucleophiles has not yet been shown. A novel catalytic activation of various O, N, and C nucleophile–silicon bonds using tBu‐P4 base was investigated to perform nucleophilic reactions with various electrophiles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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“…[27] The introduction of even the minimally bulky trimethylsilyl (TMS) group onto tert-alcohols is non-trivial and often inefficient using TMS-Cl under standard Lewis base promoted conditions, e.g. TMS-Cl (1.2 eq.…”

Section: Entrymentioning

confidence: 99%

Amines vs. N‐Oxides as Organocatalysts for Acylation, Sulfonylation and Silylation of Alcohols: 1‐Methylimidazole N‐Oxide as an Efficient Catalyst for Silylation of Tertiary Alcohols

Murray

Spivey

2015

Adv Synth Catal

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A comparison of the relative catalytic efficiencies of Lewisbasic amines vs. N-oxides for the acylation, sulfonylation and silylation of primary, secondary and tertiary alcohols is reported. Whilst the amines are generally superior to the N-oxides for acylation, the N-oxides are superior for sulfonylation and silylation. In particular, 1-methyl-imidazole-N-oxide (NMI-O) is found to be a highly efficient catalyst for sulfonylation and silylation reactions. To the best of our knowledge, NMI-O is the first amine or N-oxide Lewis basic organocatalyst capable of promoting the efficient silylation of tertalcohols in high yield with low catalyst loading under mild reaction conditions.

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Selective Deprotection of Silyl Ethers

Cited by 265 publications

References 0 publications

Enantioselective Total Synthesis of Wieland-Gumlich Aldehyde and (−)-Strychnine

Enantioselective Total Synthesis of Wieland-Gumlich Aldehyde and (−)-Strychnine

Catalytic Activation of Silylated Nucleophiles Using tBu‐P4 as a Base

Amines vs. N‐Oxides as Organocatalysts for Acylation, Sulfonylation and Silylation of Alcohols: 1‐Methylimidazole N‐Oxide as an Efficient Catalyst for Silylation of Tertiary Alcohols

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